Not sure when this was added. When you have a Bluetooth-enabled phone that is set up and in-range of your Mac, the caller ID information will show up on the Mac screen when the phone rings!

In addition to the caller ID info, there are three buttons that allow you to forward the call to voice mail, answer the phone, or send an SMS message to the caller. I can't find preferences anywhere to turn this on and off, it just is. I am using a Sony Ericsson t68i phone with T-Mobile service, and an AmbiCon USB bluetooth adapter on an 800MHz eMac, running the latest system (10.2.5).

I have a T68i with Rogers and a D-Link USB Bluetooth adapter
all runnng on a G4 with 10.2.5 an I don't get this feature
appearing on my computer. Do you have to have the phone
linked to the computer to have this feature enabled?

I've been using this since MacWorld, but it has been available since Jaguar came out.
When you paired your phone to your system, it asked what services you want to share (Contacts, Calendar, Internet).
As long as you have the Address Book open, and your phone in range, it will act as caller id and allow you to click on a phone number and have your phone dial automatically.
A catch, however, is that is you leave your system and come back, the link is broken. You will hve to either hit the bluetooth button in the address book, or restart the program.

I'm using the Sony Ericsson Clicker, which has a built-in proximity sensor. There's a script included that re-connects address book functionality when you come back into range.

Well I just figured out that if you have the Sony clicker installed
you have to make sure that it is turned off or else you aren't
able to use your address book at the same time.
So I finally got it to work.

The 3650 seems so much more extensible than the T68i. It has support for JaveME programs and a lot of memory to store those programs on. Perhaps someone should start working on whiping up a *better than* SonyEricsson Clicker program??

I was tempted to buy a Nokia 3650 because of all the features and bluetooth of course at such a low price point. I have 2 friends that work at Cingular, cell-phone service provider akin to AT&T, T-Mobile in case you haven't heard of it. Friend 1 told me that Friend 2 demoed for Friend 1 the bluetooth feature on the 3650 and it only worked with voice-only devices, such as a headset. It did not do data-transfer over bluetooth. Friend 1 has a T68i was unsuccessful at connecting with the 3650. Friend 2 is very knowledgable when it comes to most things technology and has a laptop, so I assume he tried it with that, but I don't know for sure.

Speaking as a former Nokia owner I'd say that the BT on Ericsson is less a hassle than the Nokias. The BT on t68i, e.g., uses no fancy-schmancy tricks to connect to a headset while the Nokias demand a Nokia-brand headset.
Apple and the t68i is a match made in heaven!